# State the four criteria required for a good estimate

25) State the four criteria required for a good estimate.29) If a sample size of 121 is chosen then what would be the actual degrees of freedom?30)If we found a confidence interval of 45.2 to 75.3 , then what would be the margin of error?31) For college bound high school juniors, math scores on the PSAT are normally distributed with a mean of 41.2 and standard deviation of 9.1.Find the probability of a randomly selected subject from this population scoring between 35.6 and 56.0.32) If 100 subjects are randomly selected from this population, find probability that their mean score is between 40.4 and 41.6.33) The distribution of the ages of U.S. commercial aircraft is normally distributed and has a mean = 18.2 years and a standard dev. = 10.9 years. If the FAA randomly selects 45 commercial aircraft for special stress tests, find the probability that the mean age of this sample group is greater than 15.0 years.34) If the FAA randomly selects 45 commercial aircraft for special stress tests,find the probability that the mean age of this sample group is at least 19 years.35) The heights female athletes have a mean = 69 inches and a standard dev. = 9 inches. If all possible random samples of size 85 are taken from this population, determine:The standard deviation (standard error)of the sampling distribution (DSM)36) The percent of sample means that between 68.2 and 69.2537) The probability of a sample mean is below 69.55 inches.38 Below what sample mean can we expect to find the lowest of 20 percent of all sample means?39) A population of scores has a mean = 8.4 and a standard deviation of 1.50 Assume its distribution is approximately normal. If a score is randomly selected, find the probability that it is greater than 7.00.40) If 32 different scores are randomly selected find the probability their mean is greater than 8.241) If 35 different scores are randomly selected find the probability their sample mean being at most 8.8.42) Nationally, a new mountain bike has a mean selling price of $834 with standard deviation = 85. Assume the selling price of this bike is normally distributed. What is the probability of a bike having a price of $900 or more?43)If 100 different bikes are randomly selected find the probability their mean price is greater than $845 ?44)If 400 different bikes are randomly selected find the probability their sample mean being less than $83045) Last years, the mean batting average of all major league baseball players was 272 and a standard deviation = 23 points. Assume batting averages are normally distributed. What is the probability that the mean of a random sample of 36 baseball players is at most 270?46) What is the probability that the mean of a random sample of 64 baseball players is at most 274?47) In the total population, 80% of all the baseball players have an average less than what value?48) A sample of 52 major league soccer players had an average height to be 69 inches with a standard deviation of 4 inches. Assume the population is normally distributed.Since this is all sample data which distribution should we use to form a confidence interval? 49 What is the 99% confidence interval for the baseball player s height?50 How large a sample is required if one would like to be 95% confident that the estimate of the population mean height is within 0.4 inches of the population mean. (Assume the population standard deviation is 5 inches)